Telephone-transmitter



(No Model.)

' D.DRAWBAUGH. TELEPHONE TRANSMITTER.

Patented Aug. 19, 1884.- Ely! INVENTOR MW ATTORN 7 ESSES w UNITED STATESPATENT OFFICE.

DANIEL nnAWBAUeH, or EBERLYS MILL, PENNSYLVANIA, ASSIGNOR TO THE PEOPLESTELEPHONE COMPANY, or NEW YORK.

To all? whom it may concern.-

TELEPHONE-TRANSMITTER.

SPECIFICATION forming part of Letters Patent No. 303,628, dated August19,1884.

Application filed March 27, 1884. (No model.)

Be it known that I, DANIEL DRAWBA GH, of Eberlys Mill, Cumberlandcounty, Pennsylvania, have invented a new and useful Improvement inTelephone-Transmitters, of which the following is a specification.

The invention relates to a telephone-transmitter wherein two'fixedelectrodes and one movable electrode are employed, the movable electroderesting upon the fixed electrodes by gravity; and it consists moreparticularly in the construction of said movable electrode.

In the accompanying drawings, Figure 1 is a front View of atelephone-transmitter with the diaphragm removed, showing the movableelectrode in place. Fig. 2 is a sectional view of said instrumenttransversely through the electrodes. Fig. 3 represents the movableelectrode separately.

In other applications for Letters Patent now pending, more particularlyin an application filed April 25, 1882, Serial No. 59,482, and incertain Letters Patent now granted to me, I have fully described andclaimed the construction of a telephone-transmitter containing threeelectrodes, preferably of carbon or other low conducting material, oneof these electrodes being fixed to the diaphragm, the second electrodebeing attached to a suitable support, these two electrodes havingoppositely-beveled faces, and'a third and loose electrode resting uponthe beveled faces of said fixed electrodes by gravity, and suchconstruction I do not herein claim. I have hitherto shown the loose ormovable electrode as a solid block of carbon or other suitable materialin cylindrical or prismatic form. In my present invention the movableelectrode is not a solid block, but consists of a hollow cylinder of anelastic non-conducting material, such as india-rubber coated on itsexterior only with carbon. I accomplish this coating by finelypulverizing the carbon and making .it into a thick paste with rubbervarnish or other suitable cement, which paste I apply by any suitablemeans to the outside of the elastic cylinder.

Referring more particularly to the drawings,A is the back board of atelephonic transmitter. B is the inclosing-box or case adapted carbonelectrode,G.

to receive on its front side a diaphragm, a por tion of which is shownat C, Fig. 2. This diaphragm may be of wood. To its rear side is secureda metal bracket, D, which contains a solid carbon electrode, E, havingan upper beveled side. To the back board, A, or the rear of the box orcase, is secured another metal bracket, F, containing a similar beveledResting by gravity upon these electrodes G and E is the hollowcylindrical electrode H, which consists, as already stated, of a hollowcylinder, (preferably of india-rubber,) I, and an outer coating ofcarbon, J. This coating of carbon, when the cement hardens, is dry andflexible. The electrode H is prevented from falling out of place whenthe instrument is moved about by the bar K, having insulated material onits lower side.

The arrangement of circuits in this instrument is the same as alreadydescribed in many of the instruments for which patents have already beengranted to me, the local battery being connected to the binding-posts 1and 2 and the circuit passing through the primary of the induction-coilM and the electrodes. The secondary of the induction-coil com1nunicateswith the line binding-posts 3 and 4 and the binding-posts 5 and 6, towhich a re ceiving instrumeut may be attached.

I find that when an elastic electrode. as

herein described, having a carbon coating is combined with the otherelectrodes, as shown, the instrument is more sensitive to speech thanwhen a solid movable electrode is employed.

I do not limit myself to two solid fixed electrodes, as hererepresented, in the sense that they must be solid blocks ofc'arbon,inasmuch as I have shown and described in other applications nowpending fixed electrodes for telephones consisting of merely a coatingof carbon or other suitable material applied, for example, to a base ofmetal, which may be a plate. Neither do I limit myself to a hollowelastic electrode. inasmuch as I may construct the same of a solidcylinder of soft rubber, for example, covered with my carbon compound orother conducting coating.

I claim as my invention 1 l 1. In a telephone, a fixed non-elasticelectrode supported upon or vibrated by the (ha 3. In a telephone, twofixed electrodes, havphragm or sound-receiving surface, a second inginclined faces, and a loose elastic tubular fixed non-elastic electrodesecured to a supelectrode having an outer coating of couductport, and aninterposed loose elastic electrode ing material resting upon said fixedelectrodes I resting upon the "fixed electrodes by gravity, by gravity,substantially as described. substantially as described.

2. In a telephone, a hollow electrode of DANIEL DRAXVBAUG H. elasticmaterial, in combination with and resting loosely by gravity upon theinclined \Vitncsses: IO faces of two fixed electrodes, substantially asPARK BENJAMIN,

described. J. B. CHURCH.

Lil

